Electromagnetically operated valve

ABSTRACT

A valve for controlling fluid flow having a chamber of non magnetizable material having an inlet opening and at least one outlet opening, a magnetizable armature having a valve closure member, an electromagnetic drive for moving the closure member from one end to the other of a path defined by the chamber. A seating is provided at each end of the path within the chamber, each seating being complementary to the external surface of the closure member, so that the closure member is a snug fit in each seating. A permanent magnet and pole pieces create two opposite, spaced apart powerful magnetic fields in each of which the flux extends across the chamber perpendicular to the direction of movement of the closure member, and a solenoid surrounds the chamber, which when energized creates a second magnetic field, in which the flux is parallel to that of the permanent fields.

FIELD OF INVENTION

This invention concerns electromagnetically operated valves forcontrolling or directing fluid flow, typically gas flow, although theinvention can be applied to the control of liquids.

BACKGROUND TO THE INVENTION

It has been proposed to move a valve closure member by the linearmovement of a magnetic armature by alternating the flux gradient inmagnetic field acting on the armature. An arrangement is described inBritish Patent Application No. 9923744.8

It is an object of the present invention to provide an improved designof valve chamber so that the fluid pressure acts to assist in keepingthe valve closure member against a seating to close an exit from thechamber.

SUMMARY OF THE INVENTION

According to the present invention there is provided a valve forcontrolling fluid flow comprising:—

-   (1) a chamber of non magnetisable material having an inlet opening    and at least one outlet opening.-   (2) a magnetisable armature comprising a valve closure member,-   (3) an electromagnetic drive for moving the closure member from one    end to the other of a path defined by the chamber,-   (4) first passage means communicating with at least the inlet    opening for supplying fluid under positive pressure to the chamber    and second passage means communicating with the at least one outlet    opening,-   (5) a seating at each end of the path within the chamber, each    seating being complementary to the external surface of the closure    member, so that the closure member is a snug fit in each seating,    said at least one outlet opening being located in or adjacent one of    the seatings, so that positioning the closure member in that seating    closes off the outlet and prevents fluid from leaving the chamber    via the second passage means,-   (6) permanent magnet means and pole pieces for creating two    opposite, spaced apart powerful magnetic fields in each of which the    flux extends across the chamber perpendicular to the direction of    movement of the closure member,-   (7) solenoid means surrounding the chamber which when energised    creates a second magnetic field, in which the flux is parallel to    that of the permanent fields, and-   (8) circuit means adapted to cause current to flow in one direction    or the other in the solenoid, whereby the second field will    reinforce the flux in one of the permanent fields and reduce it in    the other, thereby to cause the armature to move from the weaker    field to the stronger and thereby move from one seating to the other    so as to change the state of the valve.

The valve may be arranged to control the flow of fluid from the inlet tothe one outlet passage and movement of the closure member from theseating containing the outlet opening to the other seating allows fluidto flow from the chamber along the second passage means, whilst movementof the closure from the other said seating, to the first seating, blocksthe outlet opening so that no fluid can leave the chamber.

The valve may include a second outlet opening communicating with a thirdpassage means, the second outlet opening being located in or adjacentthe said other seating so that movement of the closure between theseatings causes fluid to leave the chamber either via the second passagemeans or the third passage means.

Spring means is preferably provided which in the absence of magneticforces, will centre the closure member in the chamber midway between theseatings.

The spring means may for example act between the closure member andopposed ends of the path in the chamber.

In such an arrangement movement of the closure into one of the seatingsunder the influence of a change in the overall magnetic field caused bya current flowing in the solenoid, causes one of the springs to becompressed more than the other, so that when a reverse current issupplied to the solenoid, the potential energy stored in the morecompressed spring acts to move the closure member towards the other endof its travel within the chamber.

Alternatively and preferably the closure member is acted on by at leastone leaf spring which can flex from a mid-position one way or the otherto accommodate the closure member's travel, and provide a restoringforce acting towards the mid-position when flexed.

Preferably the inner ends of the pole pieces are shaped so as also to becomplementary to the surface shape of the closure member, but areadapted to ensure that a small air gap exists between the closure memberand the relevant pole pieces when the closure member has moved into eachseating.

Alternatively a layer of non-magnetic material is provided on thesurface of the closure or pole-pieces, or both, so that the closurecannot come into touching contact with the pole pieces.

Alternatively the gap or thickness of the layer of non-magnetic materialis selected so that the flux concentration in the air gap ornon-magnetic layer is sufficient to retain the closure member at thatend of its travel even after current ceases to flow in the solenoid, butis such that the new magnetic field produced by the solenoid when thelatter is energised by an oppositely polarised current, is sufficient toovercome the magnetic force acting on the closure, to cause it to moveto the opposite end of its travel.

A flow restrictor may be located in the inlet passage to the chamber.

The chamber may be arranged so that the path of movement of the closureis generally horizontal or generally vertical.

The chamber conveniently may be orientated so that the closure is at thelower end of its travel when it closes off the opening leading to anoutlet passage, so that gravity assists in the closure of the outletopening.

The armature closure member may be solid, or may be hollow to reduce itsmass.

The magnetic pole-pieces may be external of the chamber, and the chamberwall is of reduced thickness in the regions of the pole pieces.

The pole-pieces may extend into and partially through the chamber wall,and the reduced thickness of the chamber wall provides a tin layer ofnon-magnetic material to prevent the armature closure member from cominginto contact with the magnetic material of the pole pieces when it is atone end or the other of the path.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of example with reference tothe accompanying drawings, in which:

FIG. 1 is a diagrammatic side elevation in cross-section of a valveembodying the invention,

FIG. 2 is a diagrammatic top view, also in cross-section, of the valveof FIG. 1,

FIG. 3 is a diagrammatic end elevation also in cross-section of thevalve of FIG. 1, and

FIG. 4 is a perspective view, to an enlarged scale, of the closuremember and leaf springs and shaft on which the closure can rotate.

DETAILED DESCRIPTION OF THE INVENTION

In the drawings, items 10 and 12 are powerful permanent magnets and polepieces 14, 16, 18 and 20 concentrate the magnetic field into two regionsat opposite ends of a chamber 22 within which a part spherical valveclosure member 24 is held captive, but is free to move within thechamber from one end to the other under the influence of variations inthe magnetic field.

These variations are brought about by passing an electric currentthrough a coil 26. When the current flows in one direction the fluxbetween 14 and 16 is reinforced and that between 18 and 20 is depleted.When the current flows in the opposite direction the effect on the twofluxes is reversed.

The valve closure 24 is formed from magnetisable material and may besolid or hollow, and will tend to be attracted to the region of maximumflux density, and can be thought of as an armature.

If the current flow produces the higher flux density between poles 14and 16, the armature closure member will move so as to occupy the gapbetween 14 and 16. By forming the inner surfaces of the pole pieces withcomplementary part spherical surfaces, the air gap between the polefaces 14, 16 and the closure 24 can be very small, thereby maintaining avery high flux density between 14, 16 even when the current flow ceases.Accordingly the closure 24 will remain between 14, 16.

If current in the opposite direction flows in the winding 26, thereduction in flux between 14, 16 is arranged to be sufficient to “free”the closure 24 and allow it to move so as to occupy the position at theopposite end of its travel between poles 18, 20. By forming these withsimilar part spherical inwardly facing faces, and ensuring that theremaining gaps between 18, 20 and the closure 24 are very small (asbefore in the case of 18, 20), when the current ceases to flow, theclosure will now remain between poles 18, 20 until such time as currentin the appropriate sense is caused to flow in the winding 26 to producean appropriate magnetic flux gradient and cause the armature closure 24once again to move to the position between 14, 16.

The movement of the closure is made more reliable by centering theclosure by means of leaf springs 28, 30, so that when the latter is atone end the springs 28 and 30 are flexed in one direction and when theclosure is at the other end the springs are flexed in the oppositesense.

As shown in FIG. 4, the springs extend through slots 25, 27 at oppositeends of a cylindrical shaft 29 on which the armature closure 24 isrotatable, and the springs bend one way or the other to allow 24 to movefrom one end to the other of the chamber 22.

The magnetic field is concentrated by the use of magnetic flux returnpaths 32, 34 separated at their ends from magnetic material blocks 36,38, 40 and 42 by non-magnetic material spacers 44, 46, 48 and 50. Theblocks 36-42 serve as pole extensions to the pole pieces 14, 16, 18 and20 but the relatively large effective air gaps between for example 32and 36 at one end and 32 and 38 at the other end, tends to ensure thatmagnetic flux which might otherwise leak from the outer ends of the polepieces is retained in a closed magnetic circuit, thereby increasing theflux concentration in the gaps between 14 and 16 and between 18 and 20.

The chamber is formed from a non-magnetic material such as plastics oraluminium.

In the wall of the chamber are two openings, 52, 54 which allow theinterior of the chamber to communicate with the passages, 56, 58, bothof which can serve as fluid outlets from the chamber.

Opposite openings 52, 54 is another opening 60 also in the chamber wallwhich allows the interior of the chamber to be supplied with fluid froma pressurised fluid source (not shown) via an inlet passage 62. A flowrestrictor 64 may be located in the passage 62. The region around eachof openings 52 and 54 is complementary to the spherical shape of closure24, so that if the closure is located over either opening 52 or 54, anypositive pressure within the chamber will tend to press the closureagainst the complementary surface and thereby seal the opening andpassage beyond (i.e. 58 in the case of opening 54) from the interior ofthe chamber. In this case, passage 52 freely communicates with theinterior and fluid entering the chamber from 62 can pass out throughopening 52 into passage 56.

If passage 56 is blocked off, then fluid is in fact prevented fromleaving the chamber.

The valve can thus be converted from a diverter valve (diverting fluidfrom 58 to 56 or vice versa depending on which of openings 52 and 54 arecovered by the closure) to a single on/off valve by blocking off 56 (or58).

A flow restrictor (not shown) may be located in either or both of 56 and58 if desired to increase the pressure in the chamber.

One of the outlet openings 52 can be seen (in hidden detail) in FIG. 2together with the outlet passage 56, and opposite can be seen the inletopening 60 and inlet passage 62. A restrictor 64 is shown in FIG. 3 inthe inlet port 63 leading to passage 62.

Being a cross-section, lower pole pieces 18 and 20 and magnets 10 and 12are also visible in FIG. 2.

Although not shown, if the path of movement of the closure 24 isgenerally vertical, gravity can be employed to assist in retaining theclosure at the lower end, shutting off the outlet. Any failure of themagnetic circuit would tend to allow the closure to drop under gravity,making the valve fail safe (under gravity and if provided the effect ofany spring acting in a downward sense.

Additional sealing force can be provided by additional leaf springs suchas 68, 69 (see FIG. 4) acting on the shaft 29.

1. A valve for controlling fluid flow comprising: (1) a chamber of nonmagnetisable material having an inlet opening and at least one outletopening, (2) a magnetisable armature comprising a valve closure member,(3) an electromagnetic drive for moving the closure member from one endto the other of a path defined by the chamber, (4) first passage meanscommunicating with at least the inlet opening for supplying fluid underpositive pressure to the chamber and second passage means communicatingwith the at least one outlet opening, (5) a seating at each end of thepath within the chamber, each seating being complementary to theexternal surface of the closure member, so that the closure member is asnug fit in each seating, said at least one outlet opening being locatedin or adjacent one of the seatings, so that positioning the closuremember in that seating closes off the outlet and prevents fluid fromleaving the chamber via the second passage means, (6) permanent magnetmeans and pole pieces for creating two opposite, spaced apart powerfulmagnetic fields in each of which the flux extends across the chamberperpendicular to the direction of movement of the closure member, (7)solenoid means surrounding the chamber which when energised creates asecond magnetic field, in which the flux is parallel to that of thepermanent fields, and (8) circuit means adapted to cause current to flowin one direction or the other in the solenoid, whereby the second fieldwill reinforce the flux in one of the permanent fields and reduce it inthe other, thereby to cause the armature to move from the weaker fieldto the stronger and thereby move from one seating to the other so as tochange the state of the valve.
 2. A valve as claimed in claim 1 whenarranged to control the flow of fluid from the inlet to the one outletpassage and movement of the closure member from the seating containingthe outlet opening to the other seating allows fluid to flow from thechamber along the second passage means, whilst movement of the closurefrom the other said seating, to the first seating, blocks the outletopening so that no fluid can leave the chamber.
 3. A valve as claimed inclaim 1 further comprising a second outlet opening communicating with athird passage means, the second outlet opening being located in oradjacent the said other seating so that movement of the closure betweenthe seatings causes fluid to leave the chamber either via the secondpassage means or the third passage means.
 4. A valve as claimed in anyof claims 1 to 3 further comprising spring means which in the absence ofmagnetic forces, will centre the closure member in the chamber midwaybetween the seatings.
 5. A valve as claimed in claim 4 wherein thespring means acts between the closure member and opposed ends of thepath in the chamber.
 6. A valve as claimed in claim 4 or 5 whereinmovement of the closure into one of the seatings under the influence ofa change in the overall magnetic field caused by a current flowing inthe solenoid, causes one of the springs to be compressed more than theother, so that when a reverse current is supplied to the solenoid, thepotential energy stored in the more compressed spring acts to move theclosure member towards the other end of its travel within the chamber.7. A valve as claimed in any of claims 1 to 4 wherein the closure memberis acted on by at least one leaf spring which can flex from amid-position one way or the other to accommodate the closure member'stravel, and provide a restoring force acting towards the mid-positionwhen flexed.
 8. A valve as claimed in any of claims 1 to 7 wherein theinner ends of the pole pieces are shaped so as also to be complementaryto the surface shape of the closure member, but are adapted to ensurethat a small air gap exists between the closure member and the relevantpole pieces when the closure member has moved into each seating.
 9. Avalve as claimed in any of claims 1 to 7 wherein a layer of non-magneticmaterial is provided on the surface of the closure or pole-pieces, orboth, so that the closure cannot come into touching contact with thepole pieces.
 10. A valve as claimed in either of claims 8 or 9 whereinthe gap or thickness of the layer of non-magnetic material is selectedso that the flux concentration in the air gap or non-magnetic layer issufficient to retain the closure member at that end of its travel evenafter current ceases to flow in the solenoid, but is such that the newmagnetic field produced by the solenoid when the latter is energised byan oppositely polarised current, is sufficient to overcome the magneticforce acting on the closure, to cause it to move to the opposite end ofits travel.
 11. A valve as claimed in any of claims 1 to 10 wherein aflow restrictor is located in the inlet passage to the chamber.
 12. Avalve as claimed in any of claims 1 to 11 wherein the chamber isarranged so that the path of movement of the closure is generallyhorizontal.
 13. A valve as claimed in any of claims 1 to 11 wherein thechamber is arranged so that the path of movement of the closure isgenerally vertical.
 14. A valve as claimed in claim 13 in which thechamber is orientated so that the closure is at the lower end of itstravel when it closes off the opening leading to an outlet passage, sothat gravity assists in the closure of the outlet opening.
 15. A valveas claimed in any of claims 1 to 14 wherein the armature closure memberis solid.
 16. A valve as claimed in any of claims 1 to 14 wherein thearmature closure member is hollow to reduce its mass.
 17. A valve asclaimed in any of claims 1 to 16 wherein the magnetic pole-pieces areexternal of the chamber, and the chamber wall is of reduced thickness inthe regions of the pole pieces.
 18. A valve as claimed in claim 17wherein the pole-pieces extend into and partially through the chamberwall, and the reduced thickness of the chamber wall provides a thinlayer of non-magnetic material to prevent the armature closure memberfrom coming into contact with the magnetic material of the pole pieceswhen it is at one end or the other of the path.